[PATCH 1/2] nand_base: SOFT_BCH: Request strength over bytes
Boris Brezillon
boris.brezillon at free-electrons.com
Wed Jan 14 01:34:49 PST 2015
Hi Aaron,
On Mon, 12 Jan 2015 18:35:55 -0600 (CST)
Aaron Sierra <asierra at xes-inc.com> wrote:
> Previously, we requested that drivers pass ecc.size and ecc.bytes when
> using NAND_ECC_SOFT_BCH. However, a driver is likely to only know the ECC
> strength required for its NAND, so each driver would need to perform a
> strength-to-bytes calculation.
>
> Avoid duplicating this calculation in each driver by asking drivers to
> pass ecc.size and ecc.strength so that the strength-to-bytes calculation
> need only be implemented once.
>
> This reverts/generalizes this commit:
> mtd: nand: Base BCH ECC bytes on required strength
Apart from the nit below, you can add my:
Reviewed-by: Boris Brezillon <boris.brezillon at free-electrons.com>
>
> Signed-off-by: Aaron Sierra <asierra at xes-inc.com>
> ---
> drivers/mtd/nand/nand_base.c | 21 +++++++++++++++------
> drivers/mtd/nand/sunxi_nand.c | 2 --
> 2 files changed, 15 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index 41585df..993612c 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -4028,22 +4028,31 @@ int nand_scan_tail(struct mtd_info *mtd)
> ecc->read_oob = nand_read_oob_std;
> ecc->write_oob = nand_write_oob_std;
> /*
> - * Board driver should supply ecc.size and ecc.bytes values to
> - * select how many bits are correctable; see nand_bch_init()
> - * for details. Otherwise, default to 4 bits for large page
> - * devices.
> + * Board driver should supply ecc.size and ecc.strength values
> + * to select how many bits are correctable. Otherwise, default
> + * to 4 bits for large page devices.
> */
> if (!ecc->size && (mtd->oobsize >= 64)) {
> ecc->size = 512;
> - ecc->bytes = DIV_ROUND_UP(13 * ecc->strength, 8);
> + ecc->strength = 4;
> }
> +
> + /*
> + * We previously recommended drivers pass ecc.size and
> + * ecc.bytes. Continue to support drivers that do.
> + * See nand_bch_init() for details.
> + */
> + if (ecc->bytes && !ecc->strength)
> + ecc->strength = ecc->bytes * 8 / fls(8 * ecc->size);
How about fixing all NAND_ECC_SOFT_BCH users (AFAICT the only remaining
one is nandsim, since you fixed sunxi_nand) instead of keeping this
backward compat code.
Best Regards,
Boris
--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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